Why are humans altruistic?

Why would we act to help others, even to our own detriment? That concept -- altruism -- has become a long-standing mystery for philosophers and scientists alike. Under evolutionary theory, it makes little sense. If we're driven to ensure our genetic survival through reproduction, then any altruistic instinct should emerge only after we've successfully reproduced. Even then, it should only be displayed toward offspring and other blood relatives who share the same genetic line. Yet, strangers help one another out of danger. Altruism flies in the face of economic theory of rational maximization, which says that when it comes to money and resources, humans should act selfishly, taking as much as they can for themselves and leaving only as much for others as they must. Yet, the presence of charities and studies of charitable giving show that humans don't always -- or even routinely -- act selfishly.

Various fields have issued a number of explanations for altruism, perhaps none more basic than the one put forth by the field of neuroscience: The reward centers in the brain are activated when we carry out an altruistic act [source: Hinterthuer]. In other words, we derive pleasure from helping others.

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This answers the age-old question of whether there is such a thing as an unselfish act; the answer is no, since we gain pleasure in return for altruism. It also uncovers a larger question: Why would our brains respond to altruistic behavior the same way it rewards us for carrying out survival behaviors, like eating or procreation? Altruism can put us in danger, like when a person pushes another from in front of a bus or comes to the aid of someone under attack. So, why are we altruistic?

Who does altruism serve?

The idea that we gain from helping others existed long before we could witness how the brain functions. Researchers pointed out that the sense of self-satisfaction we receive from helping another, along with the idea that we "bank" favors by helping others is evidence that humans are selfish. In a sense, we've confused long-term selfish acts for altruism [source: Gintis, et al].

Over time, different competing explanations for altruism have taken shape. It became clear that human generosity may be context-specific. There also may be more than one type. Reciprocal altruism, where we give under the assumption that we'll receive in return, is different from kin selection, where our altruism favors our relatives over strangers. What is sure is that altruism is a motivator, just like our emotions, our sense of curiosity, and any behaviors that our brains can activate, reward or punish. If we believe that altruism is a motivator, we still arrive back at the same question: What purpose does it serve?

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There are essentially two domains that altruism can serve: the self or the group. It's also entirely possible that it serves both.

If altruism is a motivator, then we can compare them to emotions. While the debate continues over the nature of emotions, it appears that humans may have a lower set of basic emotions like fear, joy and anger that serve the self. The other set of "higher" or "moral" emotions, like pride and embarrassment, that are specific to our interactions with others, allows us to live in groups [source: Simons].

If altruism follows this model, then we have a set of basic, self-serving altruistic behaviors as well as another, higher type that evolved as we came to live in larger groups. This would explain why we see altruistic behavior in other animals, yet can't reconcile our own altruism entirely through evolution.

The full explanation of altruism remains elusive, and one man stands as a cautionary tale for those who seek to understand it. In the 1960s, evolutionary biologist George Price created a mathematical formula for altruism -- called the Price equation -- that showed that over time, those individuals who acted exclusively in their own self interest would succumb to natural selection. Price's equation also showed that altruistic acts benefit the giver. After he completed his equation, he became a "radical altruist," donating all of his possessions to the needy and ultimately becoming destitute himself [source: Khan]. He committed suicide in a squat in London just after Christmas, in 1974.

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